v0.3.5

Added

• Per-segment metadata: vault_write() and vault_write_stream() accept optional HashMap<String, String> metadata, encrypted within the index block. vault_read() returns SegmentReadResult { data, metadata }.
• Segment rename: vault_rename_segment(old_name, new_name) updates the index without re-encryption. WAL-protected for crash safety. DuplicateSegment error variant added.
• Index caching: in-memory dirty flag tracks index mutations. Read-only operations skip redundant index encryption/flush. New vault_flush() API for explicit durability control.
• Parallel reads: vault_read_parallel(handle, names) decrypts multiple segments concurrently via rayon + mmap zero-copy. Returns per-segment SegmentResult { name, data, error }.
• Dart VaultService wrappers: renameSegment(), flush(), readParallel(). Updated write()/writeStream() to accept optional metadata parameter. Updated read() to return SegmentReadResult.
• 15 Dart integration tests covering metadata (4), rename (4), flush (2), parallel read (3), and combined workflows (2).
• Rust test suite refactored from monolithic tests.rs into 13 focused modules. 407 total Rust tests.
• Example app: metadata input field, rename dialog, flush button, parallel read all button.

Changed

• VAULT_VERSION bumped 1 → 2 for backward-compatible metadata deserialization (v1 vaults return empty metadata).
• ARCHIVE_VERSION bumped 1 → 2 for metadata preservation in export/import (v1 archives import with empty metadata).
• vault_write_file now passes metadata through to vault_write_stream (was hardcoded to None).
• vault_close() flushes dirty index before releasing lock, with best-effort WAL checkpoint on error.

Security

• Metadata encrypted within the index block (AEAD with index key), not in the segment cipher — no plaintext leakage.
• OOM guards: MAX_METADATA_PAIRS (1024) and MAX_METADATA_BYTES (64 KB) enforced on both read and write paths.
• Parallel reads use immutable &VaultHandle — no shared mutable state between threads. Compile-time Sync assertion.
• Checked offset arithmetic in parallel mmap slicing (checked_add instead of bare +).
• Plaintext zeroized on all checksum failure paths in parallel reads.

Fixed

• Async error assertions in Dart rename tests changed from expect() to await expectLater().
• Example app evfs_test.dart updated for SegmentReadResult return type.